Extensions to OSPF for Temporal LSPdraft-chen-ospf-tts-02

Internet Engineering Task Force H. Chen
Internet-Draft Huawei Technologies
Intended status: Standards Track M. Toy
Expires: January 21, 2018 Verizon
V. Liu
China Mobile
L. Liu
Fijitsu
July 20, 2017
Extensions to OSPF for Temporal LSPdraft-chen-ospf-tts-02.txt
Abstract
This document specifies extensions to OSPF for distributing Traffic
Engineering (TE) information on a link in a sequence of time
intervals.
Status of this Memo
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Internet-Draft OSPF for Temporal LSP July 20171. Introduction
Once an existing multiprotocol label switching (MPLS) traffic
engineering (TE) label switched path (LSP) is set up, it is assumed
to carry traffic forever until it is down. When an MPLS TE LSP
tunnel is up, it is assumed that the LSP consumes its reserved
network resources forever even though the LSP may only use network
resources during some period of time. As a result, the network
resources are not used efficiently. Moreover, a tunnel service can
not be reserved or booked in advance for a period of time.
This document specifies extensions to OSPF for supporting the setup
of an MPLS TE LSP in a period of time called a time interval or a
sequence of time intervals. It is assumed that the LSP carries
traffic during this time interval or each of these time intervals.
Thus the network resources are efficiently used. More importantly,
some new services can be provided. For example, a consumer can book
a tunnel service in advance for a time interval or a sequence of time
intervals. Tunnel services may be scheduled.
2. Terminology
A Time Interval: a time period from time Ta to time Tb.
LSP: Label Switched Path. An LSP is a P2P (point-to-point) LSP or a
P2MP (point-to-multipoiint) LSP.
LSP in a time interval: LSP that carries traffic in the time
interval.
LSP in a sequence of time intervals: LSP that carries traffic in each
of the time intervals.
Temporal LSP: LSP in a time interval or LSP in a sequence of time
intervals.
TEDB: Traffic Engineering Database.
This document uses terminologies defined in RFC2328 and RFC3630.
3. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119.
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Internet-Draft OSPF for Temporal LSP July 20174. Representation of TE Information
The existing Open Shortest Path First (OSPF) Traffic Engineering (TE)
distributes an unreserved bandwidth Bi at each of eight priority
levels for a link at one point of time, for example, at the current
time.
Bandwidth
^
|
Bi|______________________________________________________
|
|
-+------------------------------------------------------> Time
|
This means that the link has bandwidth Bi at a priority level from
now to forever until there is a change to it. This TE information on
the link is stored in TEDB.
Thus, a temporal LSP (i.e., an LSP in a time interval) cannot be set
up using the information in the TEDB and the bandwidth cannot be
reserved in advance for the LSP in the time interval.
To support temporal LSPs, we should extend OSPF to distribute TE
information on a link in a series of time intervals.
4.1. TE Information in Absolute Time
Suppose that the amount of the unreserved bandwidth at a priority
level on a link is Bj in a time interval from time Tj to Tk (k =
j+1), where j = 0, 1, 2, .... The unreserved bandwidth on the link
can be represented as
[T0, B0], [T1, B1], [T2, B2], [T3, B3], ....
This is an absolute time representation of bandwidths on a link.
Time Tj (j = 0, 1, 2, ...) MUST be a synchronized time among all
network nodes.
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Bandwidth
^
| B3
| B1 ___________
| __________
|B0 B4
|__________ B2 _________
| ________________
|
-+-------------------------------------------------------> Time
|T0 T1 T2 T3 T4
If an LSP is deleted or down at time T and uses bandwidth B, then for
every time interval/period (after time T) during which bandwidth B is
reserved for the LSP on a link attached to a network node, the
network node adds B to the link for that interval/period.
If an LSP is set up at time T and uses bandwidth B, then for every
time interval/period (after time T) during which bandwidth B is
reserved for the LSP on a link attached to a network node, the
network node subtracts bandwidth B from the link for that interval/
period.
If there are significant changes to the bandwidths on a link attached
to a network node, the network node distributes the bandwidths on the
link to other network nodes. That is that a updated [T0, B0], [T1,
B1], [T2, B2], [T3, B3], etc., are distributed to other network nodes
in the network. Each of the other network nodes can construct or
determine the bandwidth for a series of time intervals/periods on a
link after receiving the information.
4.2. TE Information in Relative Time
Alternatively, a relative time representation of bandwidths on a link
can be used. For example, the amount of the unreserved bandwidth at
a priority level on a link is Bj during a series of time intervals/
periods can be expressed as
[P0, B0], [P1, B1], [P2, B2], [P3, B3], ..., where
Pj = Tk - Tj, k = (j+1) and j = 0, 1, 2, 3, ....
In this representation, every time Tj (j = 0, 1, 2, ...) can be a
local time. A timer may expire after every unit of time (e.g., every
second) and trigger --P0, which decrements P0. When P0 = 0, P1
becomes P0, P2 becomes p1, and so on.
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Internet-Draft OSPF for Temporal LSP July 2017
If there are significant changes to the bandwidths on a link attached
to a node, the node distributes the bandwidths on the link to other
nodes. That is that a updated [P0, B0], [P1, B1], [P2, B2], [P3,
B3], ..., are distributed to other network nodes in the network. On
each of the other network nodes, a timer may expire for every unit of
time (e.g., every second) and trigger --P0, which decrements P0.
When P0 = 0, P1 becomes P0, P2 becomes p1, and so on.
An advantage of using relative time representation is that the times
or clocks on all the network nodes can be different.
5. Extensions to OSPF
This section describes the extensions to OSPF for supporting the
setup of temporal LSPs.
5.1. TE LSA
An opaque LSA of type 10 is originated by a network node to
distribute TE information such as the bandwidth of a link that is
attached to the network node.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | LS Type=10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 | Opaque ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ TLVs ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The opaque LSA comprises a link-state (LS) age field, an options
field, an LS type field, an opaque identifier (ID) field, an
advertising router field, an LS sequence number field, an LS checksum
field, a length field, and one or more TLVs.
The LS age field indicates the time since the LSA was originated in
seconds. The options field indicates the optional capabilities
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Internet-Draft OSPF for Temporal LSP July 2017
supported by the described portion of the routing domain. The LS
type field indicates the type of the LSA. The opaque ID field is a
number used to maintain multiple opaque LSAs. The advertising router
field indicates the Router ID of the router that originated the LSA.
The LS sequence number field is used to detect old or duplicate LSAs.
Successive instances of an LSA are given successive LS sequence
numbers. The LS checksum field indicates the Fletcher checksum of
the complete contents of the LSA, including the LSA header but
excluding the LS age field. The length field indicates the length of
the LSA in bytes.
5.2. TTS Link TLV
In addition to existing router address TLV and link TLV, TLVs fields
may comprise a new temporal tunnel service (TTS) link TLV.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (5) | Length (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (0) | Segment-Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub TLVs |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The TTS link TLV comprises a type field, a length field, a reserved
field, a segment-number field, and a sub TLVs field.
The type field may comprise a value assigned by the Internet Assigned
Number Authority (IANA) to indicate that the TLV is a TTS link TLV.
For example, the type field may comprise a value of 5. The length
field may indicate the length of the values in the TTS link TLV in
bytes.
The segment-number indicates a segment of the TTS link TLV. The
information on a link may be too big to fit into one TTS link TLV.
In this case, the information may be split into a few of segments,
each of which is put into a TTS link TLV and identified by a segment
number.
The sub TLV field comprises a link type sub-TLV and a link ID sub-
TLV. It may further comprise a local address sub-TLV, a remote
address sub-TLV, a TE metric sub-TLV, a maximum bandwidth sub-TLV, a
maximum reservable bandwidth sub-TLV, an unreserved bandwidth sub-
TLV, an administrator group sub-TLV, a relative TTS unreserved
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